Grand Caravan FWD V6-3.3L VIN 3 Flex Fuel (2002)
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vehicle's odometer reads more than 5 miles.
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engine speed is above 500 rpm.
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coolant temperature is below 66 °C (151 °F).
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fuel tank has greater than 1/8 of a tank of fuel.
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Power switch on the Automatic Temperature Control is on.
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Driver Temperature Control on the Automatic Temperature Control is set above 22 °C (72 °F).
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Front Control Module (FCM) sees the Cabin Heater Activation request that is bussed from the Automatic Temperature Control.
When the DCHA starting sequence begins, the glow plug and the combustion air fan are activated.
After 30 seconds, the fuel dosing pump begins operating and the combustion air fan operation is suspended for 3 seconds. Subsequently, the
combustion air fan speed is increased in two ramps within 56 seconds to nearly full load operation. After a stabilization phase of 15 seconds, the
combustion air fan speed is again increased in a ramp within 50 seconds to nearly full load. After reaching full load fuel delivery, the glow plug is
deactivated and the combustion air fan operation is increased to full load. During the subsequent 45 seconds, as well as in normal operation, the glow
plug functions as a flame sensor to monitor the flame condition. After all these events, the automatically controlled heating operation starts.
In case of a no flame or a flame out condition, a restart is automatically initiated. If the no flame condition persists, fuel delivery is stopped and the
heater enters an error lockout mode with a rundown of the combustion air fan. This will set one or more DTCs in the DCHA Control's memory. If six
continuous attempts to start the heater fail due to one or more faults in the DCHA system, the heater enters a heater lockout mode. This will set DTC
B1813 along with any other fault(s) that the DCHA Control identified.
Heating
During the automatically controlled heating operation, when the coolant temperature reaches 76 °C (169 °F), the heater will switch to a part load
operation. When the coolant temperature reaches 83 °C (181 °F) or if the heater runs for longer than 76 minutes the heater will switch to a control
idle period. If the coolant temperature drops to 73 °C (163 °F) during a control idle period, the heater will perform a regular starting sequence into full
load operation. A drop in coolant temperature to 66 °C (151 °F) during part load operation will cause the heater to switch to a full load operation.
Deactivation
For vehicles with a Manual Temperature Control system, the DCHA will deactivate if the:
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engine is turned off.
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coolant temperature reaches 83 °C (181 °F).
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heater runs longer than 76 minutes (for normal automatic controlled heating operation).
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heater reaches 5-minute timeout period (for once per ignition cycle operation).
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fuel tank has less than 1/8 of a tank of fuel.
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Power switch on the A/C - Heater Control Module is off.
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Blend Control on the A/C - Heater Control Module is set below 75% reheat. 5 detents
For vehicles with a Automatic Temperature Control system, the DCHA will deactivate if the:
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engine speed drops below 500 rpm.
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engine is turned off
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coolant temperature reaches 83 °C (181 °F).
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heater runs longer than 76 minutes.
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fuel tank has less than 1/8 of a tank of fuel.
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Power switch on the Automatic Temperature Control is off.
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Comfort level is attained as determined by the temperature setting on the Automatic Temperature Control.
When the heater is deactivated, the combustion stops and a run-down sequence begins. During the run-down sequence, the combustion air fan
continues operation to cool down the heater. The fan is automatically switched off after the run-down sequence is complete. The run-down time and
the combustion air fan speed depend on the heater operating condition at the time of deactivation. Run-down time is approximately 175 seconds when
deactivated in full load operation and approximately 100 seconds when deactivated in part load operation.
Diagnostics
DIAGNOSTICS
The DCHA is fully addressable with the DRBIII. System tests include a Field Mode Test to activate the DCHA for diagnostic testing purposes. The
DCHA Control will store up to three DTCs in its memory. If the Controller detects a new fault in the DCHA system, one that is not already stored in
its memory, it will clear the oldest of the three stored DTCs, and it will store the new fault's DTC. If the Controller detects a reoccurrence of a stored
fault, it will overwrite that fault's DTC with the most recent occurrence.
For vehicles equipped with Automatic Temperature Control (ATC), the AC Cooldown Test will also activate the DCHA for diagnostic testing
purposes. The AC Cooldown Test is actuated with the DRBIII. The test checks A/C system performance based on evaporator temperature sensor
input. It also forces the ATC to initiate a Cabin Heater Activation request when the vehicle is equipped with a Diesel Cabin Heater Assist (DCHA).
The air conditioning related portion of this test will not run if ambient temperature is below 12 °C (53 °F). However, the forced Cabin Heater
activation will occur even if the air conditioning portion of this test fails to initiate because test criteria was not met. The air conditioning related
portion of this test will pass if the evaporator temperature drops 6.7 °C (20 °F) within two minutes of starting this test. Only air conditioning related
messages display on the DRBIII after running this test. These messages will clear after paging back out of this test. Therefore, it is important to note
